Approximately 70% of the Earth's surface is covered by water, yet much of the subsea world remains largely unexplored. Ocean observatories currently rely on the use of tethers or cables connected to ships on the surface of the water to transmit high bandwidth data. Such use of tethers restricts mobility and limits the ocean depths that can be explored due to limitations on the length of the tether. Acoustic communication enables wireless transmission of information underwater but is limited by low bandwidth and high latency due to the relatively low speed of sound underwater when compared to the speed of light, due to the relatively low frequency and bandwidth of acoustic waves when compared to electromagnetic waves, and due to acoustic noise in the ocean. Electromagnetic radiation is hindered due to the high absorption of electromagnetic waves across most of the electromagnetic spectrum.
The constraints of either tethered or acoustic communication are further exacerbated by the need to transmit high quality video over a significant distance for effective subsea exploration. For example, high quality video enables more reliable inspection of oil-rigs for mechanical failure. In addition to high bandwidth transmission, a need also exists for low latency transmission to enable teleoperation. In certain applications, low latency also enables haptic feedback for robotic control in harsh environments.
In an untethered environment, a need exists to collect data from a variety of sensors on the sea floor using an unmanned underwater vehicle (UUV). The UUV is required to locate sensors to position itself to reliably receive transmitted data from the sensors and to navigate between sensors. Accordingly, there is a need for a reliable, mobile, high bandwidth and low latency underwater optical communication system that can be used for wireless communication over a significant range.